GB2304860A

GB2304860A - Tube shearing mechanism for a gate valve

Info

Publication number: GB2304860A
Application number: GB9616605A
Authority: GB
Inventors: David K Green
Original assignee: Baker Hughes Inc
Current assignee: Baker Hughes Holdings LLC
Priority date: 1995-08-08
Filing date: 1996-08-07
Publication date: 1997-03-26
Also published as: CA2182825A1; GB9616605D0; AU6196096A; NO963300D0

Abstract

The invention provides a system for shearing tubing (30) disposed in the flow passage (12) of a gate valve (10). The system includes a guillotine (14) reciprocally movable transverse to the flow passage. A pressure source (22) communicates with an actuating surface (18) of the guillotine, and a separate actuator (24) signals the pressure source to exert sufficient pressure upon the actuating surface to reciprocate the guillotine, forcing an opposed shearing surface of the guillotine (14) to flow into the flow passage and shear the tubing (30). In a preferred embodiment, the pressure source (22) is an explosive charge.

Description

:!rT"OD AND APPARATUS MECHANISM OP A GATt "Atv Field of the Invention The present invention provides a mechanism separate from that responsible for opening and closing the gate in a gate valve for shearing off coiled or rigid tubing held in the flow passage of the gate valve.

Background of the Invention Oil and gas wells are ccmpleted with a wellhead having an arrangement of valves, including those comprising the wellhead for blowout control. In the normal operating position, rigid or coil tubing extends through the wellhead valves so that the tubing can be located at the proper depth in the well. Wellhead valves typically are gate valves with a full bore opening onto a flow passage when the hole in the gate is aligned with the bore through the valve.

Typically, wellhead valves have hydraulic or air operated actuators and assorted mechanisms, such as springs, to make sure that the gate closes, and seals off the wellbore in the event of a failure. In such gate valves, a spring or similar structure provides the force necessary to open and close the valve.

Before tubing is extended through the flow passage, nothing obstructs the gate from closing off the flow passage, and the force of the spring or similar mechanism of the actuator is sufficient to close the gate. After tubing is extended through the flow passage, the tubing obstructs the flow passage and interferes with gate closure. The spring return actuator may not be powerful enough to shear off the tubing and leave an unobstructed area for closing the gate valve.

Various means to obtain the force required to shear off the tubing have been employed in the past. These approaches primarily have involved increasing the size or power of the actuator or the working pressure of the hydraulic or pneumatic fluid responsible for actuating the actuator. Unfortunately, increasing the operating fluid pressure increases the cost of the actuator because the actuator components must safely withstand the higher operating pressures. In addition, the springs that are required to close the valve may be larger and heavier than desirable. This can be a problem, especially in offshore applications, where space is a primary concern. A very bulky spring also is difficult to handle and may present maintenance problems.

An alternate, less cumbersome apparatus is needed to shear off tubing extending through the flow passage of a gate valve to permit closure of the gate valve.

Suarv of the Invention The present invention provides a system for shearing tubing disposed in the flow passage of a gate valve. The system includes a guillotine that is reciprocally movable transverse to the flow passage. A pressure source communicates with an actuating surface of the guillotine, and a separate actuator signals the pressure source to exert sufficient pressure upon the actuating surface to reciprocate the guillotine, forcing an opposed shearing surface of the guillotine to flow into the flow passage and shear the tubing.

In a preferred embodiment, the pressure source is an explosive charge.

Brief Description of the Drawings Fig. 1 illustrates in section a gate valve with the guillotine of the present invention in the open position and the gate in the closed position.

Fig. 2 illustrates in section a gate valve with the guillotine and the gate in the closed position.

Fig. 3 illustrates in section a gate valve with the guillotine in the closed position and the gate in the open position.

Fig. 4 is a plan view of the guillotine and gate valve of the present invention.

Detailed Descrivtion of the Invention The present invention provides a separate mechanism in a gate valve for shearing off tubing held in the flow passage of the gate valve. Preferably, the shearing mechanism is an explosive powered guillotine.

Fig. l shows a spring return actuated gate valve 10 having a flow passage 12. Mounted adjacent to and in alignment with the wall 13 of the flow passage 12 is a guillotine 14 with a shearing surface 16 substantially opposed to an actuating surface 18.

Opposite the guillotine 14 is the gate 20 in a closed position.

The flow passage 12 is sealed from the remainder of the gate valve 10 by seals 32. The guillotine 14 is reciprocally and sealingly mounted within a bore 25 (see Fig. 3) in a complimentary sleeve 26.

The guillotine 14 is sealed using conventional means, for example, using o-rings 28. Coiled tubing 30 extends through the flow passage 12.

Adjacent to the actuating surface 18 of the guillotine 14 is a power source 22 in communication with an actuator 24. In a preferred embodiment, the power source 22 is an explosive charge, and the actuator 24 is an igniter. The explosive charge may be any standard explosive charge. The igniter may be any standard lubricator/bleeder with electrical connections.

In Fig. 2, the gate 20 is shown, again, in the closed position. The actuator 24 has ignited the power source 22, forcing the guillotine 14 against the gate 20, thereby shearing the coiled tubing 30. Both o-rings 28 continue to maintain the seal between the guillotine 14 and the sleeve 26, and the seals 32 continue to maintain the seal between the flow passage 12 and the remainder of the gate valve 10.

Fig. 3 illustrates the operation of the guillotine 14 when the gate 20 is in the open position. When the gate 20 is open, the force exerted on the guillotine 14 by the power source 22 pushes the guillotine 14 onto the coil tubing 30 and cuts it cleanly.

This allows the coil tubing 30 to drop into the wellbore and permits the spring to move the whole gate 20 to the "closed" position, thereby permitting the gate 20 and seals 32 to mate and seal the wellbore.

Referring to Fig. 4, the guillotine 14 is seen in plan view adjacent to the flow passage 12. O-rings 28 maintain the seal between the guillotine 14 and the sleeve 26. A vent 34 may be provided between the last o-ring 28 and the pressure source 22 as a safety valve to release excess pressure that may result from actuating the power source. Of course, the vent 34 should release only excess pressure, and care should be taken to retain sufficient pressure within the bore 25 behind the actuating surface 18 of the guillotine 14 to ensure that the guillotine 14 shears any tubing in the flow passage 12.

The connection between the actuator 24 and the power source 22 is seen in more detail in Fig. 4. In a preferred embodiment, the connection 36 is an electrical connection that is integral with a plug 38 that may be inserted into the end of the bore 25 and sealingly engaged in the sleeve 26. In a preferred embodiment, shown in Fig. 4, the plug 38 and the bore 25 are provided with complimentary threads for threaded engagement between the plug 38 and the bore 25.

The guillotine 14 may be installed in a suitable gate valve 10 by machining into the gate valve 10 a bore 25 sized to form a complimentary sleeve 26 for the guillotine. The guillotine 14, surrounded by the necessary seals 28, then may be inserted into the bore 25, and the plug 38 should be engaged in the bore 25, e.g., by threading.

The explosive charge or other power source 22 should be capable of exerting sufficient force on the actuating surface 18 of the guillotine 14 to propel the guillotine 14 through any tubing extending through the flow passage 12 until the shearing surface 16 of the guillotine 14 impacts the gate 20. Other power sources 22 also may be used as long as they are capable of exerting sufficient force on the actuating surface 18 of the guillotine 14 to shear the tubing. An alternate power source 22 would be chemical reactants that react with one another to result in sufficient thermal expansion of the air adjacent to the actuating surface 18 to propel the guillotine 14 through the tubing in the flow passage 12.

Persons of skill in the art will appreciate that many modifications may be made to the embodiments described herein without departing from the spirit of the present invention.

Accordingly, the embodiments described herein are illustrative only and are not intended to limit the scope of the present invention.

Claims

CLAIMS:

1. A system for shearing tubing disposed in the flow passage of a gate valve, comprising: a guillotine having a shearing surface at one end and an actuating surface at a substantially opposed end, said guillotine being reciprocally movable in a plane of movement between an open position and a shearing position; a pressure source in communication with said actuating surface of said guillotine whereby, upon actuation, said pressure source exerts sufficient pressure upon said actuating surface to reciprocate said guillotine into said shearing position, thereby shearing said tubing and permitting closure of said gate valve; and, an actuator sealingly communicating with said pressure source.

2. The system of claim 1 further comprising an anvil abutting said shearing surface of said guillotine when said guillotine is in said shearing position.

3. The system of claim 1 wherein said pressure source comprises an explosive charge; and said actuator comprises an igniter.

4. The system of claim 1 wherein said pressure source comprises chemicals that react with one another in response to said actuator to cause gaseous expansion.

5. The system of claim 4 wherein said actuator comprises a catalyst for said chemical reaction.

6. A gate valve comprising: a body; a stem acting within said body; a guillotine having a shearing surface at one end and an actuating surface at a substantially opposed end, said guillotine being reciprocally movable in a plane of movement between an open position and a shearing position; a pressure source in communication with said actuating surface of said guillotine whereby, upon actuation, said pressure source exerts sufficient pressure upon said actuating surface to reciprocate said guillotine into said shearing position, thereby shearing said tubing and permitting closure of said gate valve; and, an actuator sealingly communicating with said pressure source.

7. The gate valve of claim 6 further comprising an anvil abutting said shearing surface of said guillotine when said guillotine is in said shearing position.

8. The gate valve of claim 6 wherein said pressure source comprises an explosive charge; and said actuator comprises an igniter.

9. The gate valve of claim 6 wherein said pressure source comprises chemicals that react with one another in response to said actuator to cause gaseous expansion.

10. The gate valve of claim 9 wherein said actuator comprises a catalyst for said chemical reaction.

11. A method for closing the gate of a gate valve after shearing tubing disposed in the flow passage of said gate valve comprising: providing a gate valve having a gate and a separate shearing structure; first actuating said shearing structure to shear said tubing: and subsequently actuating closure of said gate.